Trunking system, due to its special application and the site in which it is used, requires fast access. The paging of traditional CDMA system takes a relatively long time to perform the processes of paging, paging response, then channel assignment, and acquisition, and its access speed can not meet the requirement of trunking application. Moreover, the paging of the traditional CDMA system is performed according to the IMSI address, one paging message can only be sent to one terminal, which means serial processing is adopted by the paging terminal, so the access time for a group with a lot of users would be very long and cannot meet the requirement for rapid access of the trunking system.
So the Grouping Identifier (GID) paging mode is applied. With all terminals matching GID paging address, only one paging message is needed to page all terminals in the group; the channel resource is directly carried in the paging message and sent to the terminal while paging the terminals, it largely saves the time for calling and speeds up the access of terminal. GID refers to grouping identifier, and different groups have different GIDs. GID address refers to the paging address generated via GID and it is unique for a specific group.
Group call usually has the limitation of dispatching area, namely, a certain group can only call in a specified area (such as an area including several geographically connected cells), and the terminal is not offered with the group call of said group outside the dispatching area. For example, if a group call is initiated by one terminal, the paging message is sent simultaneously to all cells within the dispatching area of the group (usually much smaller than the ordinary paging area of CDMA), after receiving the paging message, all terminals in the group within the dispatching area establish corresponding channel resource and access the call.
After the group call is established, in the cases that a terminal in the group is turned on within the dispatching area or enters the dispatching area from a non-dispatching area and etc., the delayed access of the terminal needs to be implemented after a signal is received from the base station. Considering that the dispatching system can not detect in real time the condition of the terminal which does not access the system, the base station side should periodically or non-periodically re-send the paging message. The usual solution is that the base station periodically sends the paging message until the call ends in the process of a group calling. Since the base station periodically sends the paging message, the paging message can be received only if the terminal is in idle state in the dispatching area, and based on this, the channel resource is established and the delayed access to the system is achieved.
During the calling, the terminal subscriber may exit the group call because of certain reasons, which can be divided into two conditions: one is abnormal exit, such as the terminal drops the call when it enters into tunnel not covered with signals, under this condition, the terminal should be guaranteed to be able to re-access after it receives the paging message periodically sent; the other is normal exit, such as the terminal subscriber actively exits the group call or the dispatching system sends release signaling to the terminal to ask it to exit one call and so on, in this condition, the subscriber should remain the exit state if it does not actively re-access. But with the present processing method, since the base station periodically sends the paging message, the terminal will still passively re-access after it normally exits the call because of receiving the paging message, which brings inconvenience and disturbance to the user's use and the dispatching management.
Moreover, after the terminal normally exits, the subscriber may need to re-access the group call, which requires the terminal capable of distinguishing the two conditions, not only able to prevent from passive re-accessing the call, but also able to actively re-access.